This invention relates to the glass drawing art and, more particularly, to a machine and method for drawing out glass fibers of a uniform diameter. In the past, glass has been drawn in a machine which supports glass stock vertically from a cable or the like. A motor drive then lengthens the cable from a drum, and the stock is lowered into an oven. When the stock is heated, a glass fiber is drawn from it at a point below the oven. The oven is, thus usually a hollow cylinder, open at both ends.
In the prior art, attempts have been made to lower the glass stock into the oven at a constant velocity. This, in turn, causes diameter variations in the drawn glass. In the first place, the stock is suspended like a pendulum. Therefore, it sways to and fro. The cable also vibrates. The stock support does have guides, but the bracket holding the stock hangs up on the guides. The lowering process does not give the lowering motor a positive, constant load to work against. The stock is, thus, lowered in jerky movements. The cable is elastic and causes the stock to bounce. Further, the cable movement around the drums and pulleys is not and cannot be positively guided. Due to the extremely low velocity of the stock and the accuracy desired, a long gear train must be employed. Any shift in any gear can and does cause jerky stock movement because the motor is not working into a highly positive and sustained load.
The above-described prior art glass machine has some utility, but the glass fiber product thereof is nonuniform in the diameter along its length. In particular, its diameter runs true only within the limits of .+-.0.001 inch. This inaccuracy is a substantial source of difficulty because within the tolerance noted, much of the production of the machine is unusable.